Axial gas mixing in conical spouted beds with high density particles--颗粒学报PARTICUOLOGY

Dogan, N., Koksal, M., & Kulah, G. (2023). Axial gas mixing in conical spouted beds with high density particles. Particuology, 81, 45-57. https://doi.org/10.1016/j.partic.2022.12.008

Axial gas mixing in conical spouted beds with high density particles

Neslin Dogan ^a, Murat Koksal ^b *, Gorkem Kulah ^a *

a Department of Chemical Engineering, Middle East Technical University, Ankara, Turkey
b Department of Mechanical Engineering, Hacettepe University, Beytepe, Ankara, Turkey

10.1016/j.partic.2022.12.008

Volume 81, October 2023, Pages 45-57

Received 7 October 2022, Revised 4 December 2022, Accepted 12 December 2022, Available online 31 December 2022, Version of Record 16 January 2023.

E-mail: koksalm@hacettepe.edu.tr, gorkemk@metu.edu.tr

Highlights

• Unsteady state tracer experiments were carried out in conical spouted beds with varying angles.

• Both light and heavy particles were used.

• The axial gas mixing behavior was modeled by a 1-D transient convection-diffusion equation.

• The dispersion coefficients were found in the same range with the cylindrical spouted beds.

• Convection was found more significant than dispersion for light particles compared to heavy ones.

Abstract

Conical spouted beds operating with high-density particles (ρp > 2500 kg/m³) have recently gained attention because of their potential use as nuclear fuel coaters for next-generation nuclear reactors. In the literature, the number of axial gas mixing studies in conical and conical-cylindrical spouted beds is very limited and all axial mixing studies were carried out with relatively light particles (ρp ≤ 2500 kg/m³). Therefore, the objective of this study was to generate experimental data that can be used to explain the gas axial mixing behavior in conical spouted beds operating with both low- and high-density particles. Experiments were conducted in two (γ = 30°, 60°) conical spouted beds with three different types of particles: zirconia (ρp = 6050 kg/m³), zirconia toughened alumina (ρp = 3700 kg/m³) and glass beads (ρp = 2460 kg/m³). In order to be able to compare experimental data obtained at different conditions, a 1-D convection-diffusion gas mixing model originally developed by San José et al. (1995) was implemented to determine the axial dispersion coefficients. The results show that the axial dispersion coefficients range between 1.75 × 10^-2 m²/s and 9.35 × 10^-2 m²/s, increase with superficial gas velocity and are higher than the corresponding dispersion coefficients of fixed beds, lower than the dispersion coefficients of fluidized beds and in the same range with the cylindrical spouted beds reported in the literature. The corresponding Peclet numbers were in the range of 0.6–7.8 for all operating conditions and slightly higher Peclet numbers were obtained with glass beads indicating the relative importance of gas convective transport over gas dispersion for light particles compared to heavy particles.

Graphical abstract

Keywords

Conical spouted bed; Gas dispersion coefficient; Axial gas mixing; High-density particles

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